The present invention relates to a pneumatic pressure controlling apparatus for controlling the pneumatic pressure in an automobile tire, and more particularly, to such an apparatus capable of changing the pressure in the tire and controlling pneumatic pressure load detected at a vehicle body side.
In an automobile, the tire pnuematic pressure is controlled, if desired, in accordance with the road surface condition such as rain-wet surface snowfall and vehicle running condition such as high or low speed running. However, conventionally, the automobile must be stopped for changing the tire pressure. If high pressure is required, the automobile must be in the parked condition such as at a gasoline service station.
Further, if the tire pressure decreases to a level lower than the minimum pressure, fuel consumption may be increased. A special technique is required to detect the tire pressure at the vehicle compartment, since the tire is a rotational member. For example, in an attempt to detect the pneumatic pressure of the tire at the vehicle compartment by a pressure sensor mounted in the vehicle body side, a special sliding structure is required at a fluid passageway connecting the tire and the pressure sensor to fluid-tightly connect the totational member to the stationary member. This sliding structure must provide wear resistance as well as fluid-tightness. Therefore, in the apparatus proposed, disposed at the tire side (movable side) are the pressure sensor and a wireless transmitter which sends wireless or radio signal of detection, and disposed at the vehicle side is a receiver which receives the output signal from the transmitter.
However, according to the apparatus proposed, the resultant apparatus has a complicated structure and requires an expensive transmitter and detector. Therefore, the entire device becomes costly.